One dirty spark plug on LP 2 cylinder generator

[sheepfarmer]

I have a Dayton standby generator about 35 years old. It had its spark plugs changed for the first time about 3 years ago. The plugs were pretty clean still at that time. It had had a bunch of starting problems re!ated to the sensors and bad teeth in the starter motor gears. After those were fixed, and it took several tries, over 2 years, it was auto starting fine most of the time, but sometimes it would start up, die and have to restart once or twice. Yesterday generator tech changed the plugs and one was dirty. Both were gapped correctly. What if anything does one dirty plug say about engine? It runs well once started.

Going to replace with a larger generator, but don't want to sell old one to some unsuspecting soul if it is on its last leg so to speak. If it were a diesel I'd say it needed a fuel filter change, but being propane it doesn't have one. I was told when I got it that it wouldn't need new spark plugs often because propane ran so clean.

Comments? It has been a great generator. .

 

[Tughill Tom]

Dirty how? Oil soaked, burn( brown, tan) since a LP it should be a bit on the tan color. Did the last set of plugs that were replaced in the correct heat range?

 

[Fordtech86]

Can you post a pic of them?

 

[William1]

Depends on a lot of things.With an old engine, my money is on a stuck ring. The test is a leak down test. The fix would be to pull the piston, clean the ring and the land, reassemble. I'd do both cylinders (assuming it is a twin). If the leak down test is good, then I'd look at valve seals.
Have you ruin the engine for say 30 minutes or longer? The ring can be freed with extended running sometimes. 'Fix in a bottle' is to be avoided.

 

[sheepfarmer]

Dirty how? Oil soaked, burn( brown, tan) since a LP it should be a bit on the tan color. Did the last set of plugs that were replaced in the correct heat range?

One was brown, other looked like new, not sure about oil soaked. He held them out for me to see but I didn't think to take them.

Only other symptom it has had was to smell pretty propan-y when it is running.

It exercises for about 20 minutes once a week, and been about 6 months since it has been on for hours with a load.

 

[Fordtech86]

One was brown, other looked like new, not sure about oil soaked. He held them out for me to see but I didn't think to take them.

Only other symptom it has had was to smell pretty propan-y when it is running.

sounds like the cylinder with the new looking plug isn’t firing. Did it seem to run smooth? Did they check for spark?

 

[BruceP]

sounds like the cylinder with the new looking plug isn’t firing. Did it seem to run smooth? Did they check for spark?

I agree with this assessment. Perhaps the next step is to swap the ignition coils and see if the issue moves to the other cylinder.

 

[GreensvilleJay]

I'm with BP, swap coils, see if 'fouling' follows plug or coil, but....lwrite it down though, EASY to get confused what WAS the original setup vs the NEW one.....BTDT...

 

[Fordtech86]

I would recommend this instead of swapping coils just due to what I read.

90° In-Line Spark Checker

Amazing deals on this 90° Inline Spark Checker at Harbor Freight. Quality tools & low prices.

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many other out there but if you have harbor freight close its $4.

 

[BruceP]

I would recommend this instead of swapping coils just due to what I read.

Perhaps I am wrong... but the OP did not mention any audible difference in how the engine is running. I have seen a weak coil will STILL appear OK with a spark-tester... but will misfire the plug within the combustion chamber. (Not easy to hear the misfires)

 

[BruceP]

I'm with BP, swap coils, see if 'fouling' follows plug or coil, but....lwrite it down though, EASY to get confused what WAS the original setup vs the NEW one.

Good point.

I always write a question-mark "?" on a questionable part before swapping it. In this way.... even months later, if I have troubles again, I will see that "?" and KNOW that part has already given me trouble in the past.

 

[skeets]

Just get your new one sheepfarmer and put the old on in CL as is,, and let it go at that

 

[Fordtech86]

Perhaps I am wrong... but the OP did not mention any audible difference in how the engine is running. I have seen a weak coil will STILL appear OK with a spark-tester... but will misfire the plug within the combustion chamber. (Not easy to hear the misfires)

What I got was OP had someone out to service/checkover the generator before she sells it. Service guy shows her the plugs and she is sharp enough to notice the difference and asks the question here. There is a lot of info missing. To go swapping stuff without knowing what your looking for won’t get you anywhere.

 

[sheepfarmer]

I guess a more realistic question is whether or not one dirty spark plug would imply a serious problem or not. Once it has started it sounds to my ear the same as it has for 35 years. Part of me would like to keep it in case I could find another use for it, but I can't realistically do the work on it, and parts to repair it are getting hard to find. It's also not exactly small or light. On the other hand I can't see selling someone something that will leave them in the lurch in a power failure. If I do as skeets suggests I guess "as is" in a generator that old would suggest buyer beware.

 

[Yooper]

Why put more money into it if you are going to replace it? Yeah I know, you are one of those rare people with a conscience! I am one also. But if you are honest with the person you are selling it too, let them take it from there. I have a friend who worked in the power gen business that buys generators just like yours and refurbishes them and sells them. Be honest when you post the ad. I suspect someone like my friend will snatch it up or someone who is mechanically inclined would use it for their camp or cottage.

 

[lugbolt]

propane is kinda "dirty"

most propane burners are gas burners that are converted, and most of the time the engine isn't really "ideal" for propane usage. Ideally, would want more compression ratio and more ignition lead (timing) but that's a whole other subject.

When I say it's kinda "dirty", oftentimes the regulator can get, well, dirty. Gummy sort of. Same for the mixer (aka carburetor if it has one). Regulators often need rebuilt or replaced; the diaphrams get gummy and when you take one apart, it is nas-teee! One would think propane would be "clean".

Another issue with propane is warming the regulator and sometimes the mixer. Liquid cooled engines use engine coolant circulated through it/them to warm them up. If the coolant stops circulating, the parts freeze up which can cause fuel distribution issues. Could possibly be an issue with yours? EFI engines dont' typically have these issues, but I haven't dealt much with efi propane.

 

[sheepfarmer]

propane is kinda "dirty"

most propane burners are gas burners that are converted, and most of the time the engine isn't really "ideal" for propane usage. Ideally, would want more compression ratio and more ignition lead (timing) but that's a whole other subject.

When I say it's kinda "dirty", oftentimes the regulator can get, well, dirty. Gummy sort of. Same for the mixer (aka carburetor if it has one). Regulators often need rebuilt or replaced; the diaphrams get gummy and when you take one apart, it is nas-teee! One would think propane would be "clean".

Another issue with propane is warming the regulator and sometimes the mixer. Liquid cooled engines use engine coolant circulated through it/them to warm them up. If the coolant stops circulating, the parts freeze up which can cause fuel distribution issues. Could possibly be an issue with yours? EFI engines dont' typically have these issues, but I haven't dealt much with efi propane.

It is a Briggs engine designed to run on natural gas or propane. Air cooled. The part of the propane delivery system within the housing has never been cleaned or otherwise serviced, maybe because it would be a bugger to get to. If it was taken apart to move it would be a perfect opportunity to do all these things. It has had a few new parts in the last 10 years, brushes (didn't really need them), sensors etc. Regrettably it is beyond my capabilities these days, so it does need a new home. It would be great mounted on a trailor....

 

[twomany]

I have a Dayton standby generator about 35 years old. It had its spark plugs changed for the first time about 3 years ago. The plugs were pretty clean still at that time. It had had a bunch of starting problems re!ated to the sensors and bad teeth in the starter motor gears. After those were fixed, and it took several tries, over 2 years, it was auto starting fine most of the time, but sometimes it would start up, die and have to restart once or twice. Yesterday generator tech changed the plugs and one was dirty. Both were gapped correctly. What if anything does one dirty plug say about engine? It runs well once started.

Going to replace with a larger generator, but don't want to sell old one to some unsuspecting soul if it is on its last leg so to speak. If it were a diesel I'd say it needed a fuel filter change, but being propane it doesn't have one. I was told when I got it that it wouldn't need new spark plugs often because propane ran so clean.

Comments? It has been a great generator. .

If the engine ignition is a "Single coil, double ended", it is NORMAL for one plug to have a weak spark. It all has to do with how sparks like to jump off hot plug gaps.

Solution is both to swap plugs between cylinders from time to time, or.... just replace the plugs every few years.

The K series engine on my Bolens HT-23 does this. When the one plug gets too fouled, that cylinder is slower to catch on cold weather start ups.

Worth a try, costs nothing but a time to swap sides.